A precise role has not been assigned for the non-ciliated bronchiolar (Clara) lining cell in the lung. It has been considered to release surface active material which may prevent the collapse of the bronchioles. More recently the Clara cell has been throught to be an important site of xenobiotic metabolism in the lung. Certain furans (3-methylfuran, 4-ipomeanol) have been shown to selectively destroy the Clara cell in rodents. This selective destruction can be used as a tool to investigate a physiological role for the Clara cell. To this end we are measuring indices of pulmonary function in animals previously exposed to the furans. In addition, if the Clara cell is a major site of xenobiotic metabolism, exposure to the furans and re-exposure to compounds known to be metabolically activated in the lung (e.g. benzo(a)pyrene) may produce no toxic effect there, the toxicity being manifested elsewhere in the body. In order to confine our studies solely to the lung we are using the isolated, perfused lung apparatus to investigate both pulmonary function and disposition of radioactive furans (and other compounds) in the lung using autoradiography.